Toxic co-workers arrive in all shapes and forms. There are the passive-aggressive types, the pathological liars and, of course, the bullies. If you think bullies can be found only in schoolyards, think again: As many as one-third of professionals are victims of workplace bullying, and 20 percent of these incidents cross the line into harassment, according to the Workplace Bullying Institute. Managers and team leaders must take control of these situations because bullying and other harmful office behaviors can lead to employee stress, absenteeism, low productivity and high turnover—not to mention the failure of key projects. Some incidents might even lead to lawsuits. To provide some guidance about how to handle difficult employees, we present the following nine best practices. They are adapted from a range of online resources, including the "Leadership Freak" blog and AllBusiness.com. Combined, they underscore the importance of approaching potentially destructive workers with the same kind of strategic planning that you put into a major business undertaking. The goal is to ensure that these employees have minimal negative impact on other staff, as well as business outcomes.